1. Field Of The Invention
The present invention relates generally to the field of scanners for creating digital representations of documents and the like. More particularly, the invention relates to a technique for selectively scanning desired regions or designated areas of a document. The invention also relates to a technique for automatically identifying desired regions to be scanned which permits the scanner to encode only the desired regions to the exclusion of the remainder of a document or document page.
2. Description of the Related Art
Over the last several years, considerable improvements have been made in document scanning techniques. In general, document scanners illuminate a surface of a document page and detect reflections from the surface. The radiation reflecting from the page surface is encoded digitally to form a string of data or a data set representative of the indicia appearing on the document page surface. Digital scanners of this type generally divide the scanned surface or image into a matrix of discrete picture element or pixel regions. By progressively scanning lines and columns in the matrix, the entire image is encoded. The resulting code or data may be stored and further processed, and the scanned image may be subsequently reconstructed and printed.
Digital scanners are presently employed in a wide variety of components. For example, hand-held scanners permit a user to selectively input or encode a portion of a document page by sliding an array of light emitting diodes and photodiodes, and associated encoding electronics, over a document. Full-page scanners allow documents to be similarly encoded by being placed on a flat glass plate adjacent to which a scanning diode structure moves. Sheet feed scanners allow document pages to be inserted and drawn through a series of rollers to similarly pass the document before a scanning head arrangement. Such scanners may be employed in association with personal computers, but are increasingly employed in facsimile machines, printers, copying machines, and so forth.
In scanners of the type described above, a document surface is generally fully scanned during an encoding sequence. That is, the entire surface of the document page over which the encoding photodiodes extend is detected and a data set representative of pixels in the scanned image is generated. For documents having meaningful information extending over the entire page, such scanning techniques are well suited. However, when many smaller documents are scanned, the resulting data set includes large amounts of data for regions of the image which are not of interest or which contain no useful information. If all of the information contained in the data set is retained, the resulting digital file can become quite large and unnecessarily occupy available memory space and processing time.
Several techniques have been developed to selectively reduce the size of data files of scanned images. In one technique employed in personal computers, for example, generally referred to as the “TWAIN” driver, a low resolution pre-scan operation is performed and the results of the pre-scan operation can be displayed on a computer monitor. A user can then select a limited region of the document page by reference to the pre-scanned image. A subsequent higher resolution scan can then be performed on the selected region. While this technique permits a limited region of the document to be encoded in the final scan, it inconveniences the operator by requiring feedback during the scan. Moreover, the technique is not particularly well suited to automated scanning processes, such as in copiers, facsimile machines, or multifunction scanner or printer systems. The technique is similarly impractical for highly automated office environments in which a wide variety of document scanning is to be performed in batch-type processes.
There is a need, therefore, for an improved technique for selectively scanning regions of documents. There is a particular need for a technique which would permit reduced data set sizes to be output by virtue of the reduction in the size of a scanned region to a size and configuration designated by a user. The technique would advantageously allow users to preselect regions of a document and stack work in a batch-type arrangement for sequential processing.